water pollution

Any addition to fresh or seawater that interferes with biological processes or causes a health or environmental hazard. Common pollutants include nitrates, pesticides, and sewage (resulting from poor sewage disposal methods), although a huge range of industrial contaminants, such as chemical by-products and residues created in the manufacture of various goods, also enter water - legally, accidentally, and through illegal dumping.

In December 2002, United Nations secretary general Kofi Annan launched the International Year of Fresh Water 2003. By the end of 2003, the UN estimated that around 1 billion people worldwide did not have access to safe drinking water and that two-thirds of the world's population would live under ‘water stress’ conditions by 2025 if trends were not changed.

Concern is growing over the amount of medication in drinking water, as up to 90% of a dose of antibiotics is excreted in the urine. Other drugs, from aspirin to oestrogen from the contraceptive pill, are also excreted and end up in the environment. Inevitably, some of these drugs find their way back into our drinking water.

Scientists have warned that certain pollutants present in drinking water can mimic the female hormone oestrogen and that this could have an impact on male fertility. A US study released in 2002 produced the first scientific proof that environmental oestrogens could prevent adult sperm from being able to fertilize eggs. The study showed that combinations of industrial products such as herbicides, pesticides, and synthetic paints could artificially speed up the maturity of sperm, rendering them unable to penetrate the walls of an egg.

The United Nations Environment Programme (UNEP) reported in 2003 that nutrient contamination of water supplies was causing increased environmental damage and causing the formation of extensive ‘dead zones’ for aquatic life, especially in the world's fishing areas. Excessive nutrient content in water from human activities, such as sewerage and the overuse of nitrogen-based fertilizers in agriculture, promotes the uncontrolled growth of ‘blooms’ of algae. These tiny plants fall to the seabed where they decompose, a process that starves the surrounding water of oxygen, creating a zone that does not support fish and other marine life. UNEP reported that the number of known ‘dead zones’ in the world has risen to 150 and this number had doubled every decade since monitoring began in the 1960s.

In 2003, of the 120 million tonnes of nitrogen-based fertilizer that is used globally, only 20 million was incorporated into crops while the remainder is washed into rivers and the sea.